Pen & paper roleplaying games span a large variety of different play styles. But in general they have two main parts: One roleplaying part of interactive storytelling, not unlike improvisational theatre; and one combat part where dice are rolled in some sort of turn-based tactical combat system. Yesterday there was a discussion in the comment section whether playing D&D held any challenge, or whether it was just players sitting around, shooting the breeze. Now as I said different people play these games differently, but most of the pen & paper games I have played, and especially D&D, sure had challenge.

Obviously in a pen & paper game it doesn't matter how fast you can react or roll the dice, so the challenge is very different from that of a real-time computer RPG. But it is comparable to turn-based RPG or tactical computer games. For combat to not be boring, it must fulfill two conditions: Different outcomes must be possible, and the decisions of the player must matter in determining that outcome. So assuming a decent DM running a campaign with a non-trivial amount of combat, there is at the very least challenge during combat, a pressure on the player to make the right tactical decisions to make combat go their way. And ideally there is also a bit of challenge in the roleplaying part, where the strategic set-up of the encounters would be determined: Coming up with a great plan before the combat should help make that combat easier.

If different outcomes must be possible, it also means character death must be possible. Now in some systems character death can be kind of random: In early editions of D&D/AD&D a level 1 wizard had 1-4 hitpoints, while a simple arrow did 1-6 points of damage. One stray arrow and you were dead. 4th edition D&D has combatants with more health compared to the amount of damage dealt, making combat slower, but also more tactical. More dice rolls means less dependence on a single lucky or unlucky roll, and more influence of player decisions. But unless the DM cheats, a mix of bad decisions and bad rolls can still very much kill a character.

The reason why some DMs cheat to prevent character death is that they value the story part of the game higher than the tactical part. In terms of story, a character death is messy, especially if your story is on the scripted side: If you built a campaign around one of your characters being the long lost heir to the kingdom, you don't want that character to die. But personally I have always found that the strength of a roleplaying game is its improvisational style, and that a certain amount of randomness does help. If the rogue decides to sneak past the guard, his skill check to move silently determines how the story continues. That prevents the story from becoming too predictable, for both the players and the DM.

Thus personally I believe that a D&D campaign in which character death is possible is better. It adds challenge to the combat part, and creates a wider variety of possible outcomes for the roleplaying part. I'd rather live with the risk of certain story arcs getting broken by some character dying than with the possibility of combat without excitement turning into a "kill 10 foozles" chore.